Spawning schedule of the imperiled Bigeye Chub (Hybopsis amblops) in Illinois

Abstract The Bigeye Chub (Hybopsis amblops) once inhabited streams and rivers in eastern and southeastern Illinois and was thought to be extirpated in the state by the 1970s. However, it was rediscovered in the 1990s from the Little Vermilion River. Today, H. amblops has become widespread and locally abundant in streams of the Wabash River drainage. Currently, little is known about the spawning and reproductive ecology of H. amblops. We conducted a study in the Salt Fork Vermilion River to determine the spawning schedule and microhabitats of H. amblops. Based upon near-weekly samples in May and June in 2019 and 2021, we determined H. amblops spawns in moderate water velocity over sandy gravel substrates when water temperatures are between 18–22 °C. Understanding such ecological traits is necessary for the continued success of H. amblops throughout its range.